1. Field of the Invention
The present invention relates to an apparatus for making coiled springs.
2. Statement of the Prior Art
Conventional coiled spring making apparatuses rely upon one of two basic systems for forming coiled portions.
According to one system called the core shaft type system, a wire is held around a core shaft including lugs thereon, which is then turned simultaneously with its axial movement to wind up the wire in a close- or pitch-coiled manner, and arms extending from both ends of the coiled portion are formed by a tool at the forming section, followed by winding-off into the coiled spring product.
According to another system referred to as the bending die system, feed rollers with a wire held therebetween are rotated to continuously feed out the wire through a wire guide and force it upon a bending die for coiling to form the coiled spring product. Alternatively, before or after that, the wire is intermittently fed out to form an arm or arms extending from one or both ends of the coiled portion by a tool at the forming section, thereby making the coiled spring products.
Most of conventional coiled spring making apparatuses substantially follow such basic systems. In general, however, the ends of coiled springs are processed into desired shapes at a forming section arranged in such a form as surrounding a coiling section before and/or after the forming of the coiled portions. In recent years, coiled spring making apparatuses numerically controlled in various forms have been developed and are now prevailing as main installations throughout the industry. Currently available are, for instance, an apparatus with built-in single spindle numerical controls wherein only the driving of a core shaft is numerically controlled to allow it to follow and synchronize with the driving of a conventional mechanical type of forming section at high speeds, an apparatus wherein the driving of a core shaft and a pitching mechanism are numerically controlled by two spindles for operative association with a pneumatic or hydraulic program sequence system of forming section, an apparatus wherein the driving of feed rollers and the driving of a main shaft to rotate several types of specific cams at the same time and angle for the actuation of several types of tools at a forming section are numerically controlled by two spindles, an apparatus wherein the driving of feed rollers and the operation of main tools at a forming section are numerically controlled by five or six spindles at the same time, and so on.
Of such several types of coiled spring making apparatuses apparatus, the core shaft system of the coiled spring making apparatus can operate at twice to triple the production rate of the bending die system of the apparatus, partly because arm forming can be carried out after a wire has been positively wound around the core shaft and partly because various forming tools can be mechanically operated at considerably high speeds and in an assured manner since dimensional accuracy during forming can be determined in consideration of their sizes and disposition. The former apparatus have an additional advantage of being inexpensive. However, the core shaft system of the coiled spring making apparatus involves the following problems. When both arms are to be formed, not only are much time and skill required for preparatory steps including the determination of the disposition and timing of actuation of forming tools and the selection and regulation of cams to actuate them but, in most cases, visual inspection is also needed for the whole pieces after forming, since to pick up a wire in a stable manner tends to be insecure for reason that lugs provided on the core shaft to hold the wire can be easily wearable. In addition, the diameter of a coiled portion obtained by winding the wire around the core shaft, followed by winding-off, tends to be unstable in terms of dimensional accuracy, since it is in an enlarged state where there are variations in the amount of springing back due to the properties of the starting wire (variations in its tensile strength and its own peculiarities). Moreover, it is impossible to control the orthogonal angles of both arms attached to coiled springs.
On the other hand, the bending die system of the coiled spring making apparatus have the following merits. Since forming is carried out with a wire successively fed out of one end, how to operate at the respective steps is easy to understand and most tools and cams of the forming section can be standardized. Moreover, it is possible to control the orthogonal angles of both arms extending from both ends of a coiled spring. Thus, a short length of time and some skillfulness are only needed for preparatory steps and selection, so that even a technician having an elementary knowledge can well operate such apparatus. Unlike the aforesaid core shaft system, it is further possible to form tension or torsion coiled springs of various geometries. (It is here understood that some tension coiled springs may be produced even by the core shaft system). However, this system has the following productivity and cost problems. The production rate of coiled springs drops considerably because of its relying upon the step of feeding a wire successively out of one end through the predetermined length, which is to be intermittently interrupted, and having a need of synchronizing a double spindle servomotor. In addition, when a second arm is to be formed after the coiled portion of a coiled spring has been formed, it is inevitably required that the coiled portion be swung by a tool at the forming section only through an angle at which that arm is to be formed. Thus, because of fears that the reference point of load of the coiled spring may depart from the specified tolerance and the angle of bending of the second arm to be formed may be unstable, the production rate of coiled springs need to be lowered. Such production rate should also be brought down for another reason that it is required to set torque at a relatively high level, since the load upon the servomotor suffers from a large change from zero to a high due to primary operations of bending wires directly and sharply, thus making the synchronism of two-spindle numerical control unstable in view of the driving characteristics of the servomotor. Such drawbacks are added by high price of the apparatus.
Thus, the conventional apparatus for making coiled springs have both advantages and disadvantages, and the coiled spring making industry now does not only suffer chronically from expert storage but is also increasingly required to supply a variety of articles made on an experimental basis to cope with diverse aspects of society. In urgent need is, therefore, the achievement of a coiled spring making system which can cope with producing a greater variety of coiled spring products in small quantities at reduced costs of production, while making it possible to make coiled springs at higher rates with rapid preparatory arrangements but with no need of skilled hands.
In order to cope with such problems as mentioned above, an object of the present invention is to provide a coiled spring making apparatus in which:
a coiling section is disposed adjacent to a forming section to process a terminating end of a coiled spring, thereby performing the forming of the coiled spring at the coiling section and the forming of the terminating end and/or an arm of the coiled spring at the same time and in parallel.
The forming section being operable to grip the coiled spring formed at the coiling section just after forming and progressively feeding the coiled spring, as gripped, to a plurality of stages where it is progressively formed into a completed coiled spring product.
More specifically, while forming the coiled spring at the coiling section, the coiled spring is formed at the progressive forming section disposed adjacent to the coiling section at the same time as and in parallel with the coiling section regardless of the number of steps of processing the ends of the coiled spring. In order to allow such a coiled spring making system to function satisfactorily, even w hen coiled springs of various length and shapes are formed at the coiling section, the coiled springs differing in the direction of turning of the coiled portions and the diameter, length, number of turns and pitch of coils and including at their leading and terminating ends arms which may be reduced to zero in length, the coiled springs can stably and securely be gripped directly with members for gripping and progressively feeding the coiled springs at the progressive forming section. In addition, forming occurring at the respective stages can be carried out without trouble, and the coiled spring formed at the coiling section can stably and securely be located at a grip position on the progressive forming section. Thus, even a technician having an elementary knowledge can easily work out preparatory steps and make coiled springs at high production rates.